1. Field of the Invention
The invention relates to thermoelectric coolers, and more particularly, to improved structures and control circuitry for thermoelectric coolers.
2. Description of the Prior Art
Portable ice boxes or coolers are widely used by hunters, campers, fishermen, motorists, etc. However, such portable ice coolers are usually used because there are no better available alternatives to their use. Portable ice coolers have numerous shortcomings. For example, they are very heavy when loaded with ice. They become filled with water as the ice melts, sometimes causing perishables stored therein to become spoiled or become water logged. Frequently, it is very inconvenient for the prior ice coolers or even impossible to obtain more ice when it is needed, so perishables consequently become spoiled. It often is a bothersome task to chip or break an ice block so that it will fit into a particular cooler. Small, front-opening ice boxes frequently have been installed in recreational vehicles, and suffer from the same shortcomings. Further, with the advent of extremely high gasoline prices, nowadays every attempt is being made to reduce the overall weight of recreational vehicles. Thus, the high weight of ice for use in ice boxes is quite unacceptable in modern recreational vehicles. The high weight of compressor-type refrigerators or liquid propane powered refrigerators mitigates against their use in modern recreational vehicles. Further, the cost of compressor refrigerators or liquid propane powered portable refrigerators is very high.
Accordingly, it is an object of the invention to provide a convenient, low cost lightweight portable cooler.
Another object of the invention is to provide a low cost, lightweight, efficient refrigerator unit suitable for installation in recreational vehicles, which refrigerator unit is substantially lighter than liquid propane powered or compressor operated refrigerators.
A number of portable coolers or refrigerators utilizing solid state thermoelectric or Peltier elements have been utilized for refrigerating units, including portable refrigerating units. However, various difficulties have been encountered providing low cost thermoelectric refrigerating units, especially for use in units mounted in recreational vehicles. One prior unit for recreational vehicles provides both external and internal heat exchangers and a fan and control unit in the front door of the unit. This device has been found to be unsatisfactory for a number of reasons, including high weight of the door, and due to inefficient operation due to location of the internal heat exchanger in a location which is exposed to warm outside air when the door is opened.
Accordingly, it is another object of the invention to provide an improved thermoelectric refrigerator which can be conveniently installed in a recreational vehicle and which provides efficient operation utilizing only a single front ventilation grill.
Prior portable thermoelectric coolers or refrigerator units and also prior thermoelectric refrigerators designed for installation in recreational vehicles have utilized over-simplified control systems having various shortcomings. One shortcoming of prior control circuitry is that it does not provide suitable indication when a voltage of a battery powering the unit has fallen below a predetermined voltage level. Another shortcoming of prior control units is that they allow the devices to be only operated as coolers, whereas occasionally it is desirable that the unit be utilized to maintain the contents of the device at a predetermined warm temperature.
Accordingly, it is another object of the invention to provide an economical control system for a thermoelectric refrigerator which enables the thermoelectric refrigerator to operate as either a refrigerator or a heating device.
It is yet another object of the invention to provide a battery powered thermoelectric refrigerator having a control system which includes a convenient means of alerting the user of a low battery voltage condition.
Another shortcoming of previous thermoelectric refrigerators is that destruction of their control circuitry and also their solid state thermoelectric devices can occur if the external heat exchangers become too hot due to blockage of ventilation of the external heat exchangers.
Accordingly, it is another object of the invention to provide a thermoelectric refrigerator having control circuitry which prevents overheating of the external heat exchanger of the thermoelectric refrigerator.
A novelty search directed to the present invention uncovered the following patents, which are believed to accurately represent the state of the art pertinent to the invention: U.S. Pat. Nos. 4,007,600, 4,107,934, 3,194,023, 4,089,184, 4,055,053, 3,973,938, 3,839,876, 3,205,657, 3,171,261, 3,123,980, 3,121,998, 3,107,324, 3,077,079 and 3,031,855.
It is another object of the invention to provide an efficient, lightweight, inexpensive thermoelectric refrigerator unit which overcomes the shortcomings of the above prior art.